This invention relates to polyether copolymers. More particularly, the invention relates to poly(aryl ether/thioether) segmented block copolymers and to the preparation of such segmented block copolymers.
Poly(aryl ethers/thioethers) are well-known resinous materials for which there are numerous commercial applications. They have good thermal and mechanical characteristics, and exhibit a wide range of other physical properties. Poly(aryl ethers/thioethers) may be categorized as amorphous or crystalline. The crystalline polymers are exceptionally chemically resistant, costly, generally insoluble in common organic solvents, and have generally low glass transition temperatures which limits their use temperatures. By contrast, the commercially available amorphous poly(aryl ether/thioethers) generally have higher glass transition temperatures and are less costly, but are also less resistant to organic solvents.
Attempts to modify the properties of poly(aryl ether/thioether) resins by blending with other polymeric materials are quite often unsatisfactory because of the incompatibility of the poly(aryl ether/thioethers) with other resinous materials. To overcome this problem, it has been proposed to polymerize one poly(aryl ether/thioether) with other poly(aryl ethers/thioethers) in order to produce poly(aryl ether/thioether) segmented block copolymers. For example, the desirable characteristics of poly(aryl ether ketones) and poly(aryl ether sulfones), e.g., solvent resistance and high glass transition temperature (T.sub.g), may be achieved by preparing a poly(aryl ether) segmented block copolymer containing both chemical groups.
Methods for preparing random poly(aryl ether) copolymers are known. Poly(ether ketone) and poly(ether sulfone) have been copolymerized by a displacement reaction, utilizing a diaryl sulfone solvent, as disclosed in "Synthesis and Properties of Polyaryletherketones", T. E. Attwood, et al., Polymer, 22, 1096 (1981). However, attempts to prepare block copolymers were unsuccessful. In "Synthesis and Characterization of Poly(Arylene Ether Ketone Sulfone) Copolymers", S. D. Wu, et al., J. Am. Chem. Soc. Polymer Prep. 227, Vol (26)2 (1985), two processes were disclosed. The first combined poly(aryl sulfone) oligomers with difluorobenzophenone monomers in an N-methyl-2-pyrrolidinone solvent, to prepare a poly(aryl ether ketone sulfone) alternating copolymer. The article described this process as simple "chain extension". The poly(aryl sulfone) oligomers were subject to ether exchange, resulting in randomization of the copolymer. The second process produced alternating copolymers from difluorobenzophenone and chlorophenylsulfone monomers, reacted together in a diphenyl sulfone solvent. Likewise, ether interchange promoted randomization of the copolymer.